Thermally assisted pulsed electro-magnetic field stimulation device and method for treatment of osteoarthritis

ABSTRACT

A method, apparatus and a system for thermally-assisted pulsed electromagnetic field stimulation for treatment of osteoarthritis are disclosed. In one embodiment, the system comprises a multi-coil applicator adapted for positioning near or around of the treated joint, a pulse generator functionally coupled to the applicator, a power supply, and a feedback loop for stabilizing the temperature of the joint. The feedback loop includes a heating element, a temperature sensor and an electronic controller for maintaining the temperature of the joint in the range of 38 to 42 degree C. At elevated temperatures the healing effect of PEMF stimulation on the cartilage is maximized and overall efficiency of the treatment is improved. To produce a high electric field, the coils of the applicator are made with a low number of turns, for example less than 5 turns, and are spatially arranged to cover the whole joint without “dead” zones.

PRIORITY

This application is a continuation of international applicationPCT/US2011/050858, filed Sep. 8, 2011, and also claims benefit of U.S.Provisional Patent Application Ser. No. 61/467,968, filed Mar. 25, 2011.This application is also a continuation-in-part of U.S. patentapplication Ser. No. 12/878,028, filed on Sep. 8, 2010 which claimspriority benefit of U.S. Provisional Patent Application Ser. No.61/276,512, filed Sep. 14, 2009. All of the above-mentioned applicationsare hereby incorporated herein by reference in their entirety.

FIELD

The invention relates to a method and apparatus for pain management,anti-inflammation and treatment of osteoarthritis. More particularly,the invention relates to an apparatus for producing pulsedelectromagnetic field in arthritic joints, and a method for treatingosteoarthritis utilizing pulsed electromagnetic fields.

BACKGROUND

Osteoarthritis (OA), sometimes called degenerative joint disease, is achronic disorder associated with damage to the articular cartilage andsurrounding tissues and characterized by pain, stiffness and loss offunction. OA commonly affects the hands, spine, and large weight-bearingjoints, such as the hips and knees. OA affects nearly 21 million peoplein the United States, accounting for 25% of visits to primary carephysicians. 80% of US population have radiographic evidence of OA by age65, and 60% of those are symptomatic. In the United States,hospitalizations for osteoarthritis soared from 322,000 in 1993 to735,000 in 2006.

Articular cartilage is the smooth white tissue that covers the surfaceof all the synovial joints in the human body. Its main function is tofacilitate the movement of one bone against another. With thecoefficient of friction as low as 0.003 and the ability to bearcompressive loads as high as 20 MPa, articular cartilage is ideallysuited for placement in joints, such as the knee and hip. Articularcartilage is composed mainly of water (70-80% by wet weight). Itcontains specialized cells called chondrocytes that produce a largeamount of extracellular matrix composed of collagen, chondroitin andkeratan sulfate proteoglycan. Collagen forms a network of fibrils, whichresists the swelling pressure generated by the proteoglycans, thuscreating a swollen, hydrated tissue that resists compression. Cartilageis one of the few tissues in the body that does not have its own bloodsupply. For nutrition and release of waste products chondrocytes dependon diffusion helped by the pumping action generated by compression ofthe cartilage. Compared to other connective tissues, cartilage grows andrepairs more slowly.

In addition to proteins and proteoglycans that comprise theextracellular matrix, the chondrocytes produce the enzymes causingdegradation of the matrix. This way the chondrocytes maintain apermanent turnover and rejuvenation of the cartilage.

The chondrocytes and the cartilage matrix change with advancing age. Thechondrocytes are responsible for both the production of new matrixproteins and the enzymes related to the cartilage degradation. It isgenerally accepted that the osteoarthritis process includes alterationsin the normal balance between synthesis and degradation of articularcartilage and the subchondral bone. In younger individuals thechondrocytes are capable of the appropriate maintenance of the cartilagetissue and keeping it healthy and functional. But with advancing age,the chondrocytes become incapable of providing adequate repair and theprocess is tipped towards degeneration.

For many years healthy cartilage tissue not only preserves its integrityand function but also performs a constant remodeling to meetrequirements of changing loads on the joints. Multiple regulatorypathways by which chondrocytes in articular cartilage sense and respondto the mechanical stimuli have been discovered in recent studies. One ofthe pathways is a mechanical one, in which the chondrocytes sense thepressure on the cartilage and respond by gene transcription, translationand post-translational modification of the extracellular matrix. Anotherpathway is a cellular response to the electrical signals generated bythe loaded cartilage tissue. It was discovered that an electricpotential appears on a cartilage tissue if it is mechanically stressed.It was shown also, that the electric signal on a loaded cartilage tissuecan be produced by two physical phenomena: a piezoelectric effect and astreaming potential.

Piezoelectric effect is the ability of some materials to generate anelectric field in response to applied mechanical stress. Piezoelectriceffect has been observed in a number of soft and hard tissues (includingcartilage and bone) and appears to be associated with the presence oforiented fibrous proteins such as collagen. A deformation of a proteinmolecule produces asymmetric shift of the opposite electric chargescomprising the molecule and results in a macroscopic electric potentialon the stressed tissue.

A streaming potential is produced when a liquid is forced to flowthrough a capillary or porous solids (including cartilage and bone). Thestreaming potential results from the presence of an electrical doublelayer at the solid-liquid interface. This electrical double layer ismade up of ions of one charge type which are fixed to the surface of thesolid and an equal number of mobile ions of the opposite charge whichare distributed through the neighboring region of the liquid phase. Amechanical stress applied to such a system creates a flow of the mobileions with respect to the fixed ions on the solid which constitutes anelectric current. The electric potential on the tissue generated by thiscurrent is called a streaming potential.

Whatever the relative contribution of these two mechanisms is in theelectric signal on the stressed tissue, a substantial electric potentialis created across the loaded cartilage. It has been suggested that thisstress-generated potential (SGP) may play a significant role incartilage growth, repair, and remodeling. Moreover, because SGP providesa link between physiology and physics it may open a new opportunity ofinfluencing biological processes in the articular cartilage. It has beenproven by numerous studies that increase in chondrocytes cell divisionand the collagen and proteoglycan synthesis are possible and may beachieved in vivo by applying electric potential to the cartilage. Thiscan be done with relatively simple medical devices. In the future thesedevices promise to become a new non-invasive modality of treatment ofarthritis and other cartilage diseases.

Currently available treatment options for osteoarthritis focus onsymptoms relief, whereas truly disease-modifying agents are lacking.Thus, the basic therapy includes common analgesics, non-steroidalanti-inflammatory drugs (NSAID), physical therapy and eventually, insevere cases, joint replacement surgery. Conventionally, physicianstreat patients exhibiting symptomatic osteoarthritis by theadministration of a NSAID. Many such non-steroidal anti-inflammatorydrugs are known and are often effective in reducing the symptoms ofosteoarthritis. NSAIDs have demonstrated ability to relieve pain,improve activity level, and in some cases improve function of thearthritic joints. None of these drugs, however, have been proven incarefully controlled clinical trials to reverse the long term naturalhistory of osteoarthritis. Moreover, while many of these drugs havedemonstrated effectiveness in treating the symptoms of osteoarthritis,they also have been associated with significant toxicities and otherrisks, such as deleterious effects on cartilage when used over prolongedperiods of time. Moreover, in addition to NSAID being very expensive,the toxicities of these drugs limit their usefulness, particularly inelderly patients. Side effects from NSAIDs could be severe; they causeover 20,000 deaths annually in US.

Appropriate exercises, including stretching, strengthening, and posturalexercises help maintain healthy cartilage, increase joint's range ofmotion and strengthen surrounding muscles so that they can absorb stressbetter. Exercises can sometimes stop or even reverse osteoarthritis ofthe hips and knees.

Heat Therapy: Heat increases blood flow and makes connective tissue moreflexible. It temporarily blocks pain, helps reduce inflammation,stiffness, and improves range of motion. Heat may be applied to the bodysurface or to deep tissues. Hot packs, infrared heat and hydrotherapyprovide surface heat. Electric currents or ultrasound generate heat indeep tissues. Research shows that heat disrupts the body's usual paincycle by stimulating heat sensors and preventing sensation of pain fromreaching the brain. Because the cartilage tissue does not have its ownpain receptors, sensation of pain in affected joints comes fromunderlying bones which are rich in pain receptors. Namely thesereceptors are blocked by the heat. As of today, there is no directevidence that the heat therapy itself can reverse or even slow downdegeneration of the cartilage affected by arthritis.

Pulsed Electromagnetic Field (PEMF) therapy is known for severaldecades. It started from observations made by several researchers inseventies decade of the last century that the pulsed magnetic field hada positive effect on healing bone fractures and damaged cartilages. Atthat time many researches believed that the healing effect was producedby the magnetic field itself and many PEMF applicators with differenttemporal and spatial patterns of applied magnetic field were claimed asbeneficial and patented. The differences between the patented featuresin the designs of the applicators and methods of treatment were in theamplitudes, lengths of magnetic pulses, their shapes, mainly rectangularand sinusoidal, repetition rates (frequencies), geometry and electricalparameters of the coils. Also, a lot of efforts and creativity weredirected to the ergonomics of the PEMF applicators and methods of theirpositioning near or securing to the human body. It was perceived thenthat the most important therapeutic parameter of the system was theamplitude of the magnetic field, so the coils were built with highnumbers of turns and the pulsed magnetic fields up to hundreds of Gausswere generated.

Alternating electrical fields for the same purpose of bone fracturehealing and treatment of damaged cartilages were exploited by severalresearch groups in laboratory studies and clinical trials. Even thoughthe electrical field applicators in these studies proved to betherapeutically effective they revealed a serious drawback—necessity toimplant electrodes into the vicinity of the treatment area or at leastapply electrodes from outside the body with electrically intimatecontact to the skin. In comparison with the electrical systems the PEMFapplicators have advantage of not only being non invasive, but also notrequiring an intimate electrical contact with the skin. Contrary to theelectric field, magnetic field at the employed frequencies easilypenetrates the human body practically to any depth.

In an electric field stimulation system developed by Brighton et all(U.S. Pat. No. 7,158,835 B2 and others of the same inventor) asinusoidal frequency of 60 kHz was employed. This relatively highfrequency allowed achieving good capacitance coupling of the treatmentvolume of the joint with the electrodes at the skin adjacent to thejoint. Clinical success of the 60 kHz system proved that the stimulatingeffect on the cartilage can be achieved with much higher frequenciesthen tens or hundreds of Hz. It can be expected that the therapeuticeffect of the electric fields on cartilage and bone healing exists in afrequency range from a fraction of Hz to up to at least 60 kHz.

Now it is common knowledge among researchers that the active agent ofthe PEMF systems is the electric field. Namely electric field interactswith biological tissues, not the magnetic field. From general theory ofelectromagnetic field it is known that an electric field accompaniesevery change in time of the magnetic field. Being more specific, theelectric field E, created by varying magnetic field, is directlyproportional to the time derivative of the magnetic inductance B. Theenergy associated with the electric field also comes from the magneticfield. It should be noted that the electric field created by a changingmagnetic field has one significant difference from the electric fieldcreated by electric charges at rest (electrostatic fields): it is acurly field, not potential as the field produced by the electriccharges. Contrary to the potential field, in which the field lines beginon positive charges and terminate on the negative charges, the fieldlines of the curl electric field are continuous; they form close loops,very much as the magnetic field lines around a wire with an electriccurrent. This nature of the curly electric field imposes somelimitations on the way the devices, whose intended use is theapplication of the electric field to human body, should be built. One ofthese limitations is the presence of areas with very low electricfields, “dead zones”. The dead zones are located near the axes of theelectromagnetic coils and produce no therapeutic effect on the treatedtissue. In details they will be discussed further herein.

In U.S. Pat. No. 5,842,966 issued to Markoll a method for treatment ofarthritis is disclosed. The method involves treating organs by applyinga magnetic field by means of an annular coil surrounding the organ, thecoil being energized by a pure DC voltage having a rectangular wave formpulsing at the rate of 1-30 CPS. The invention also includes anapparatus comprising a body support encompassed by an annular coilenergized as above. The coil is mounted on a carriage running on tracksadjacent the body support. This disclosed device and method has a deadzone along the center axis of the coil.

In U.S. Pat. No. 7,158,835 B2 issued to Brighton et al, a PEMF device isdisclosed for preventing and treating osteoporosis, hip and spinefractures, or spine fusions by incorporating a conductive coil into agarment adapted to be worn adjacent to a treatment area and applying anelectrical signal to the coil to produce a magnetic flux that penetratesthe treatment area and produces an electric field in the bones and thetreatment area. The disclosed device has dead zones along the centeraxes of the coils. The device does not include any heating means.

In U.S. Pat. No. 6,701,185 issued to Burnett et al, an apparatus forelectromagnetic stimulation of nerve, muscle, and body tissues isdisclosed. The apparatus is comprised of a plurality of overlappingcoils which are able to be independently energized in a predeterminedsequence such that each coil will generate its own independentelectromagnetic field and significantly increase the adjacent field. Thecoils are co-planar and are disposed in an ergonomic body wrap, which isproperly marked to permit an unskilled patient to locate the body wrap,on a particular part of the body, of the patient so that the stimulationcoils will maximize the electromagnetic stimulation on the selectednerves, muscles, and/or body tissues near the treated area. The devicecan be used to treat medical conditions including: muscular atrophy,neuropathic bladder and bowel, musculoskeletal pain, arthritis, as wellas possible future applications in the prevention of deep veinthrombosis and weight reduction. This PEMF device has much more uniformelectrical field than a simple coil and does not have dead zones. Thedevice does not have a heating element and does not provide PEMFtreatment at elevated temperatures.

In U.S. Pat. No. 6,179,772 issued to Blackwell a portable electronicPEMF apparatus is disclosed. The apparatus comprises a PEMF coil, powersupply, and electronic switching means. The power supply along with theswitching means provide periodic electric power to the PEMF coil. ThePEMF coil comprises multiple turns of a conductive wire around a core.The core comprises a magnetic shield layer of materials such as mu metalor soft iron. The power supply comprises a battery, a regulated voltagesource and unregulated voltage source from the battery and electronicswitching circuit. The electronic switching circuit is tuned toperiodically provide power to the coil at a frequency to generate anon-inverting, varying electromagnetic field from the coil. Disclosedapparatus also comprises a heating means. This heating means thatprovides heat to a body part under treatment is an electric resistiveheater, or, in another implementation, a chemical heater. In both casedthe applied heat is not regulated and the temperature of the treatmentarea is not controlled.

In a patent application US 20080288035 filed by Jagjit et al, astimulation device for treating osteoarthritis is disclosed. The deviceis intended for therapeutic treatment to a body part such as a joint topromote healing of the body part. It comprises a signal generator forgenerating a pulsed electromagnetic field based upon a selectedtreatment mode, a controller for storing the treatment mode andcommunicating the treatment mode to the signal generator, a heat sourceconfigured to provide thermal therapy to the body part, and monitoringmeans for monitoring the electromagnetic field generated by theelectromagnetic stimulating means. Disclosed device uses a heat or coldsource to block pain. The cold and heat sources, mainly chemical innature, are not controlled by any means; they have drifting temperaturesand do not provide PEMF therapy in the optimal range of temperatures forosteoarthritis treatment.

As noted in the above discussion, drawbacks of the existing PEMF systemsinclude: not efficient production of the electric field; not uniformcoverage of the treatment zone with the electric field, presence of deadzones. As it will be discussed further herein, from the stand point ofarthritis treatment, the PEMF systems that provide therapy at ambienttemperatures or use uncontrolled heating and/or cooling of the joint donot take advantage of providing treatment at the optimal range oftemperatures for the cartilage treatment. Therefore, there is a need foran improved device and method for treating OA that remedy the drawbacksof the prior art treatment devices and methods.

SUMMARY

The present invention effectively addresses certain drawbacks in theprior art OA treatment devices and methods. One object of certainembodiments of the present invention is to increase the amplitude ofpulsed electric field generated by PEMF systems. Another object ofcertain embodiments of the invention is to improve efficiency of PEMFtherapy for arthritis by providing more uniform spatial distribution ofthe pulsed electric fields and eliminating dead zones in the treatmentvolume. Yet another object of certain embodiments of the presentinvention is to improve efficiency of the PEMF treatment of arthritis byproviding treatment at optimal temperatures of the joints, at whichchondrocytes in the cartilage tissue have maximum metabolism andvitality.

A further object of certain embodiments is to make simple andergonomically sound Thermally Assisted PEMF treatment systems forvarious body parts, including the neck, knee, back, hand and wrist witheasy to use applicators. Another object of certain embodiments is tosimplify production of the PEMF applicator and reduce the number ofdifferent sizes of the applicators needed to be maintained for a broadvariety of patient sizes. Yet another object of certain embodiments isto provide improved heat transfer from the coils of the applicators tothe treatment area.

In accordance with one aspect of certain embodiments of the invention,electromagnetic coils producing pulsed electromagnetic field in thearthritic joints are made of a low number of turns, preferably in therange of 1 to 10 turns, more preferably in the range of 1 to 6 turns, oreven less than one full turn. In this range of numbers of turns theinductance L of the coils varies from a fraction of one micro Henry toseveral micro Henry. Assuming that the resistance of coils R is in amilliohms range, the time of relaxation of the coils L/R ranges between10 and 200 microseconds, which allows for pulse durations range about of5 to 50 microseconds. With that low inductance and short pulses even forvoltages used for powering the coils being as low as 12-24 V, the rateof change of the electric current in the coil can be extremely high, upto tens of millions Amperes per second. As a result, an electric field Einduced around the coil by the rapidly changing magnetic field willachieve tens to hundreds of mV/cm. This way of generating of electricfield is much more efficient than that with high numbers of turns andhigher inductances of the coils. The magnitude of the electric fieldabout E=100 mV/cm is a typical value of the endogenous electric fieldsgenerated by the body tissues during wound healing or during developmentor regeneration of tissues in the body. Electric field E=100 mV/cm is asafe and biologically efficient value of the electric field in the body.This value may be considered as a standard to be matched or at least tobe approached by exogenous electric fields provided by the PEMF therapy.

The PEMF coils that have only several turns and are made of multi-strandthin wires are compatible in texture with elastic fabrics and may beused for ergonomic applicators for different parts of human body.

A coil made of less than one full turn of a wire is topologicallydifferent from the coils made of several full turns. It represents anopen loop. As any open loop it can be wrapped around a joint instead ofbeing pulled over it. This feature presents an additional advantage ofenabling construction of an ergonomic PEMF applicator in which the coilcan be physically placed around a joint by simple wrapping around itwithout being stretched and pulled over it. This PEMF applicator can bebuilt, for example for knee, as non elastic wrap and still be anapplicator type “one size fits all”.

In accordance with another aspect of certain embodiments of theinvention, the PEMF applicators are configured in such a manner thatthey don't have “dead zones”, or arias in which the electric fieldinduced by the PEMF coils is too low to cause any therapeutic effect inthe cartilage. In one particular embodiment, a plurality of coils (atleast two) comprising this applicator are placed at different positionsaround or near the joint to cover all parts of the joint with anelectric field of a sufficient amplitude and right direction. The coilsmay be powered individually in sequence or in pairs in sequence. Thedirection of the induced electric field is selected mainly along thebody of cartilage, so the electric field can produce significantelectric current inside the cartilage tissue. Preferentially, the linesof the electric field should not cross the bones around the jointbecause in this case the high resistance of the bone will drasticallyreduce the current along the electric lines and there will be nosignificant current and, consequently, electric field inside thecartilage tissue. One example of an applicator inducing the electricfield in right direction is a back applicator, described below, in whichthe electric field is induced by two coils circumferentially along theintervertebral disk.

In accordance with yet another aspect of certain embodiments of thisinvention, PEMF treatment is performed at elevated temperatures of thejoint. In one implementation, the joint is heated by the ohmic heatdeposited in the coils during a pulse and by the energy stored in themagnetic field of the electromagnetic coils that is converted into heatafter the pulse. At the end of a pulse during which a coil is connectedto a DC power supply, the DC power supply is disconnected from the coiland the current through the coil is redirected into a closed loop madeby the coil and a high current diode, called a “free wheel diode”.During this time which is defined by a time of relaxation L/R of thiscircuit, the current in the closed loop is supported by the magneticenergy of the coil. The magnetic energy stored in the coil is severaltimes higher than the ohmic heat deposited during the pulse. When thecurrent through the closed loop decreases to zero, the whole magneticenergy is also deposited in the coil and the free wheel diode as heat.The free wheel diode can have a forward bias of 0.5-1.0V. When a highcurrent passes through it, a significant amount of power equivalent tothe current times the forward bias is converted into heat within thediode.

The PEMF system may include an intermediate heat exchanger which, on onehand, serves as a heat sink for the coil and the “free wheel diode”,taking heat from them and, on the other hand, as a heat pads for thejoint. The heat exchanger may comprise a dielectric material with highthermal conductivity, such as a ceramic or plastic. A feature of suchthermally assisted PEMF is that the temperature of the heating pads isstabilized in the range 39-42° C. At these elevated temperaturesmetabolism of chondrocytes is higher than at normal ambienttemperatures, so, the production of molecules of different proteins,proteoglycans, chondroitins and other important components of theextracellular matrix, substantially increases, making PEMF therapy moreefficient. It should be mentioned though, that if the temperature of thejoint for some significant time is above or equal 43° C., production ofcomponent of the extracellular matrix sharply decreases, chondrocytesstart producing so called heat proteins protecting them from heat damageand PEMF therapy becomes not efficient.

The detailed technology and preferred embodiments implemented for thesubject invention are described in the following paragraphs accompanyingthe appended drawings for people skilled in this field to wellappreciate the features of the claimed invention. It is understood thatthe features mentioned hereinbefore and those to be commented onhereinafter may be used not only in the specified combinations, but alsoin other combinations or in isolation, without departing from the scopeof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of current I(t) of the coil and its time derivativedl(t)/dt as functions of time according to an example embodiment.

FIG. 2 is an illustration of the electric field E generated by a timevarying magnetic field B(t) according to an example embodiment.

FIG. 3 is an illustration of a curl electric field E(t) produced by avarying magnetic field B(t) according to an example embodiment.

FIG.4 is a qualitative diagram of cross sectional distribution of theabsolute value of the electric field as function of a radial distancefrom the axis of the coil according to an example embodiment.

FIG. 5 is a schematics depiction of a PEMF applicator that is free ofdead zones at the treatment volume according to an example embodiment.

FIG. 6 is an illustration of the electric and magnetic fields of theapplicator according to an example embodiment comprising two coilspositioned in one plane and having electric currents in oppositedirections.

FIG. 7 is a graph of survival curves for a mammalian cell in cultureheated at different temperatures for varying length of time.

FIG. 8 a is a top view and FIG. 8 b is a side sectional view ofschematic representations of a heating pad comprising a coil, a freewheel diode and a ceramic heat sink according to an example embodiment.

FIG. 9 is a schematic representation of a PEMF system with deep heatingaccording to an example embodiment.

FIG. 10 is a PEMF system for treatment of arthritis of the handincluding the wrist, fingers and the thumb according to an exampleembodiment.

FIG. 11 is a schematic representation of a switching circuit accordingto an example embodiment.

FIG. 12 is an illustration of electric and magnetic field of two coilsat 90 degrees to each other.

FIG. 13 is an illustration of a low back multi-coil PEMF applicatoraccording to an example embodiment.

FIG. 14 is a schematic representation of two coils wound in oppositedirections according to an example embodiment.

FIG. 15 is another example embodiment of a low back PEMF applicator.

FIG. 16 is a schematic representation of electromagnetic field coverageof a human intervertebral disk and facet joints according to an exampleembodiment.

FIG. 17 is an illustration of a glove applicator according to an exampleembodiment.

FIG. 18 is an illustration of a knee applicator according to an exampleembodiment.

FIG. 19 is a schematic of one-directional and two-directional coilsaccording to an example embodiment.

FIG. 20 is an illustration of a hand applicator according to an exampleembodiment.

FIG. 21 is an illustration of a knee TA-PEMF applicator according to anexample embodiment.

FIG. 22 is another illustration of a knee TA-PEMF applicator accordingto an example embodiment.

FIG. 23 is an illustration of coils for PEMF applicators according toexample embodiments.

FIG. 24 is an illustration of a neck TA-PEMF applicator according to anexample embodiment.

FIG. 25 is another illustration of a neck TA-PEMF applicator accordingto an example embodiment.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular example embodiments described. On the contrary, the inventionis to cover all modifications, equivalents, and alternatives fallingwithin the scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

In the following descriptions, the present invention will be explainedwith reference to various example embodiments; nevertheless, theseexample embodiments are not intended to limit the present invention toany specific example, embodiment, environment, application, orparticular implementation described herein. Therefore, descriptions ofthese example embodiments are only provided for purpose of illustrationrather than to limit the present invention.

A useful understanding of the properties of the curly electric fieldgenerated by an electromagnetic coil can be achieved from an analyticalexpression for the electric current through the coil as a function oftime and analysis of the distribution of the electric field in andaround the coil.

For a coil with inductance L and resistance R connected to a DC powersupply with voltage U the current through the coil is described by aknown function of time:I(t)=U/R(1-exp(−t/τ))   (1)Where τ=L/R—is so called a relaxation time of a RL circuit.Simple differentiation of this expression gives the time derivative ofthe current:dl(t)/dt=−(U/L)exp(−t/τ)   (2)

FIG. 1 shows a graph of current I(t) and its time derivative dl(t)/dt asfunctions of time. The graph can be divided roughly in two parts, theright one for t>>τ, where the current is approaching to its ohmic limitU/R while the time derivative dl(t)/dt is close to zero, and the leftpart for t≦5τ, where the current exponentially increases from zero toalmost the ohmic limit U/R and where the time derivative sharplydecreases from the maximum value of U/L to a close to zero value. Ascurrent through the coil increases, an electric field, which isproportional to the time derivative of the current, is generated aroundthe coil. At the time t=τ the time derivative of the current and,consequently, the curl electric field generated by the coil is equal to37% of its maximum value at t=0, at the time t=0.25τ it is equal to 78%,and at the time t=0.2τ it is equal to 82% of its maximum value. As canbe seen, the generation of the curl electric field is the most efficientwhen a PEMF coil is activated by pulses not longer than 0.2τ to 0.25τ.At the end of the pulse with duration 0.25τ the maximum current Imaxthrough the coil will be dl(0)/dt×25τ=U/L×0.25L/R=0.25U/R. Therefore, toachieve efficient generation of the electric field the maximum currentthrough the coil at the end of a pulse should be aboutImax=0.25U/R   (3)

For safety reasons the operating voltage U should be below 36 Volts. Thefollowing discussion will assume that the voltage is 20V. Semiconductorcurrent switches capable of commutating currents up to 200-300 Amps areavailable on the market. The following discussion assumes a 200 Ampswitch. From formula (3) it follows that for a given voltage and maximumcurrent the required resistance should be R=0.25 U/Imax=0.025 Ohm. Thisis the resistance of the coil itself plus resistance of a switch and awiring between the coil and the DC power source.

The electric field generated by the PEMF coil can be estimated using asimple expression for the magnetic field B generated by a short circularcoil at its center.B=μ ₀ NI/D   (4)Here μ₀=4π 10⁻⁷—magnetic permeability of vacuum, N-number of turns and Dis the diameter of the coil. Differentiation of the expression (4) overtime gives us:dB/dt=μ ₀ N(dl/dt)/D   (5)Substituting expression for the time derivative of the current fromexpression (2), we will get:dB/dt=μ ₀ N(U/(L D))exp(−t/τ)   (6)For the induction of a short circular coil we can use an expression from(H. Knoepfel, Magnetic fields, John Wiley & sons, New York, 2000):L=0.5μ₀ N ² D(ln(8D/d)−7/4),   (7)where d is the diameter of the wire. After substituting (7) intoequation (6) we will get for the time derivative of magnetic inductancedB/dt:dB/dt=(U/(N D ²(ln(8D/d)−7/4)))exp(−t/τ)   (8)Inferring an expression for the electric field E induced by changingmagnetic field B of the coil can be performed using a Faraday law ofinductance:∫Edl=−d/dt∫∫BdA   (9)Here on the left is the electromotive force, a contour integral takenalong a closed loop in the magnetic field. On the right is a timederivative of a surface integral taken over a surface A pulled on theclosed loop. This surface integral is called a magnetic flux.

Generally, solution of the equation 9 requires computer simulation dueto its complexity. In the case with axially symmetric coil forintegration we can select a circular loop coaxial with the coil. If weadditionally assume that the magnetic field is uniform inside the loop,we can integrate equation 9 analytically. Because of the axial symmetryof the coil, the electric field E is also axially symmetric and can be afunction of radius r only. Remembering that, let us select for a contourof integration a circle of a radius r coaxial with the coil and lying inits plane, as shown in FIG. 2. Integration of the magnetic flux for theright side of the equation 9 can be performed over the area A which inone example is a disk with radius r, shown in the FIG. 2 as shadowed.Then we can write the equation 9 as follows:2πrE=−πr ²dB/dt   (10)Substituting expression 8 for dB/dt into equation 10 we can get for E:E=0.5r(U/(N D ²(ln(8D/d)−7/4)))exp(−t/τ) and for t=0   (11)E=0.5 τ U/(N D²(ln(8D/d)−7/4))   (12)

As can be seen from the equation 12, the electric field is proportionalto the distance from the axis of the coil r. Minimum electric field E=0is at the axis of the coil where r=0 and the maximum electric fieldE_(max) is achieved at r=D/2 of the coil:E _(max)=0.25U/(N D(ln(8D/d)−7/4))   (13)

It can be appreciated from equation 12 that a higher electric field E ina PEMF system can be achieved with higher voltages U, lower numbers ofturns N and smaller diameters D of the coils. The use of a lower numberof turns N to get a high electric field is counterintuitive toconventional thought process in the art because it is opposite to thedesire to get high magnetic field in a DC coil. In the last case, as canbe seen from equation B=μ₀NI/D, the higher number of turns, the higherthe magnetic field B is.

Nevertheless it is an instructive result that can be used inoptimization of the PEMF systems. In many conventional and priorsystems, the number of turns used is in tens and hundreds, which issuboptimal as far as the electric field generation is concerned.

A low number of turns N can be beneficially used in PEMF applicators fordifferent joints. Low number of turns means ranging from 1 to 10,preferably from 1 to 6 turns. In this range, the inductance of the coilsvaries from a fraction of one microHenry to about 10 microHenry and timeof relaxation falls between 10 and 200 microseconds, which allows forpulse durations to be in the range of 5 to 50 microseconds.

By decreasing the number of turns or diameter of the coil for theincrease of the electric field, we decrease also the duration of theelectric pulses from about several hundred microseconds routinely usedin conventional devices to 5 to 50 microseconds. Keeping in mind thatfor being efficient, a PEMF system optimally provides long enoughoverall time of application of the electric field to the treatmentvolume. Said another way, if we want to gain a higher electric field byshortening the electric pulses, to compensate for that we have toincrease their repetition rate. In previous art, as far as the pulserepetition rates in PEMF systems are concerned, a wide range from afraction of one Hertz to hundreds of Hertz had conventionally beenemployed. Repetition rates up to several tens of Hertz were preferred atearlier times because they imitated temporary patterns of real timemovements of the joints. It turned out not to be that crucial and therepetition rates up to tens of kilohertz were successfully employed. Inour case, short pulses of duration 5 to 50 microseconds a repetitionrate of several hundreds to several kilohertz may be appropriate.

If a coil having a low number of turns is made of a multistrand flexiblewire, it is also flexible and provides another advantage over highmulti-turn rigid coils: it is mechanically compatible with elasticfabrics and can be interwoven, applied, or sewn into or on them to formelastic-type applicators, for example, a “glove” applicator for thewrist and thumb, an elastic “knee hose” type applicator for treatment ofthe knee, or applicators for other joints in the body specially adaptedor configured for those joints and their movements.

Aside of the temporal pattern of the electric field induced by a PEMFcoil, another feature is its spatial distribution. Due to its axialsymmetry, the coil can create in surrounding space only axiallysymmetric magnetic and electric fields. This fact is reflected informula 12, in which the electric field E is described as dependent onlyon the distance r from the axis of the coil and is independent of theazimuthal position of the point of observation. The electric field iscurly, it is directed tangentially to the circumference at its point, asshown in FIG. 2. Also, the electric field is equal to zero on the axisof the coil and is low in the volume around it. This is substantiallydifferent from the magnetic field, which is approximately uniformthroughout the full cross section of the coil. It should be noted thatin a considerable part of the volume inside and outside the coil alongits axis the value E could be below the necessary therapeutical level.Therefore, no treatment occurs in this volume. It is a “no treatmentzone” or “dead zone”. If an arthritic lesion is located at the centeraxis of a single coil, it will not be treated. This particular featureof the electric field distribution in the PEMF coil has not beenappreciated by persons having skill in this art and is not addressed inthe designs of conventional PEMF systems.

FIG. 3 schematically illustrates the coil with a pulse current I(t) andmagnetic field B(t). A curl electric field E(t) is produced by thevarying magnetic field B(t). In FIG. 3 there is a volume in and outsidethe coil in which electric field value is below the therapeutical level.Inside the coil the shape of the “dead zone” is close to cylindricalwhile outside it increases in diameter forming a funnel shape “deadzone”. The shaded surface encompassing the dead zone is marked byletters Dz standing for a “dead zone”.

Inside the coil the dead zone has a radius r_(dz) that can be calculatedfrom the formula 12 and the value of electric field E_(min) below whichthe therapeutic effect is absent:r _(dz)=2(E _(min) /U)D ²ln((8D/d)−7/4)   (14)It can be shown that outside the coil the axial magnetic field and,hence, the induced electric field, decreases by factor (1+(2×/D)²)^(1.5)as compared with the field inside the coil. Here x is the axial distancefrom the coil to the point of observation. The radius of the dead zoneoutside the coil then will ber _(dz)(x)=2((E _(min) /U)D ²ln((8D/d)−7/4))(1+(2×/D)²)^(1.5)   (15)

The dead zone diameter outside the coil along its axis increases almostthree times at the distance from the coil equal to the radius of thecoil. It can be significant, especially for the anatomical cases inwhich the coil can not be placed around the joint but must be placed onthe patient skin adjacent to the joint. In this case the joint can beexposed to the electromagnetic field only at some axial distance fromthe coil.

The presence of a dead zone in the existing coil applicators is asignificant drawback of the current PEMF systems. In practical cases thedead zone can reach centimeters in diameter. It leaves untreated lesionsin a noticeable part of the arthritic joints. The treatment does notoccur right in the center of the coil where the magnetic field is closeto its maximum.

FIG. 4 shows a qualitative graph of cross sectional distribution of anabsolute value of the electric field outside the coil as function of aradial distance from the axis of the coil. At the axis the electricfield is zero and as the radius increases the electric field increasesand reaches its off-axial maximum approximately at the radius equal to ahalf diameter of the coil, then it steadily fades away to lower values.Also, the radius of the dead zone r_(dz), in which the electric field isless than the minimum therapeutic level Emin, is shown for low radii.

As an example, FIG. 5 exhibits a schematic representation of a PEMFapplicator free of dead zone at the treatment volume. In FIG. 5 numerals501, 503 and 505 are designated to coils, numerals 502, 504 and 506 totheir respective dead zones and numeral 507 designates the treatmentvolume. In the FIG. 5 the applicator is shown comprising 3 coils but itmay be made of plurality of coils, such as 2, 4 or more coils. The axesof coils 501, 503 and 505 may be parallel as shown in FIG. 5, or coilsmay be arranged at different angles to each other. The individual deadzones of the coils are preferably outside the treatment volume or notoverlapping in the cartilage volume. The diameters, the numbers of turnsin the coils, the distance between them and their angular positionsrelatively to the joint are selected with this requirement in mind.

As mentioned before, the electric field of the coils reaches maximumvalue at a radial distance from the axis about a half diameter of thecoil, so in the configuration shown in FIG. 5 where the coils 501, 503and 505 are positioned close to each other, each coil produces at thecenter of the treatment volume 507 maximum electric field they arecapable of generating. Sequential activation of all coils provides fullcoverage of the treatment volume 507 with the highest electric fieldachievable with each of the given coils. Activation of pairs of coilsand all three coils simultaneously can also be performed. This kind ofactivation has a different spatial distribution of the electric fieldand provides maximum electric field closer to the margin of thetreatment volume 507.

Improved coverage of the cartilage to be treated can be obtained byintroducing activation of pairs of coils positioned in one plane buthaving opposite directions of the currents. As can be seen from FIG. 6,in this case the magnetic field B at the treatment volume is not axial,it is radial relatively to the coils, and is parallel to the plane ofthe coils ZY. The electric field lines E in the treatment volume areapproximately parallel to the plane XY, which makes 90 degrees with theplane of the coils ZY. So, the contours of electric field lines, ascompared with a one coil case, change direction by 90 degrees, providinga new spatial pattern of coverage of the treatment zone outlined by thedotted line. This particular combination of two coils with oppositecurrents is particularly suitable for the applications where the coilscan not be positioned around the joint but should be secured outside thebody, as in the case of the hip, shoulder or spine. Further in thisapplication it will be disclosed how this configuration of coils can beused for PEMF treatment of the vertebral disks.

The design of the improved PEMF system disclosed herein can be furtherunderstood with regard to the following explanations.

It is generally accepted that the healing effect of the PEMF therapy iscaused only by the electric field produced by a varying magnetic field.From the electric stand point, a biological cell consists of aconductive electrolyte surrounded by a dielectric lipid membrane. If aconstant or low frequency electric field, such as used in conventionalPEMF therapy, is applied to a cell over time about one microsecond ormore, it is compensated by the movement of the ions inside the cellwhere electric field is reduced to zero. The difference of potentialthat was applied across the cell becomes applied only across thedielectric membrane. At the level of the electric field used inconventional PEMF, in the range of mV/cm, the lipid membrane staysintact, no pores are created in the membrane by the electric field, (noelectroporation effect take place), and any electric current through thedielectric lipid membrane into the cell is impossible. The electricfield inside the cell is zero. So, the electric field currently used inconventional PEMF therapy frequencies (tens of hertz to tens ofkilohertz) cannot penetrate into the cell and, consequently, can notproduce any effect on the nucleus, including gene transcription observedin PEMF therapy.

According to the improved PEMP therapy disclosed herein, during saidPEMF therapy, the electric field produces currents in the soft tissues,such as in the cartilage, and causes bombardment of the chondrocytesmembranes by ions present in the intercellular fluid. It is believedthat the mechanism at work is ion bombardment via interactions withreceptors on the surface of the membrane and ion channels through itsending a biological signal along an information pathway to the nucleusof the cell. These biological signals cause division of chondrocytes andDNA transcription in their nuclei that finally leads to production ofthe proteins, proteoglycans and other substances needed for repair ofthe cartilage.

Thus, from the preceding understanding of cartilage repair, it is notthe magnetic field, even not the applied electric field that is the mainagent producing the healing effect. It is the ion motion forced by theelectric field in the intercellular space. If in some area of thecartilage there is no current, no healing effect is expected in suchsite.

In accordance with the Faraday's law of electromagnetic inductance,(equation 9) the curly electric field induced by a PEMF system in thetissue produces an electromotive force ∫Edl along any locked contour,magnetic flux through which varies in time. Whether it creates a currentalong the contour and how high will be the current is another issue. Ina dielectric, even a relatively high electric field does not produce anycurrent. But in a good conductor it will. The current induced by thePEMF system in a human joint depends not only on the inducedelectromotive force TER, but, in accordance with Ohm's law, also on thefull electrical resistance along the contour.

If a contour crosses a layer of cartilage and a bone, electricalresistance of which is about 100 times higher than that of thecartilage, the current through this contour will be insignificantly lowand no therapeutic effect is expected in the cartilage. Because theelectrical resistivity of the bone is very high, actually only contourswhich do not cross a bone have a chance to carry a significant current.In the bulk of the bone, due to its high resistivity, practically thereare no noticeable currents. It is only the contours passing through thecartilage tissue with its relatively low resistivity that carry themajority of the electric current. In other words, the electric currentexists mainly in the cartilage layer and adjacent soft tissues. Thecurrent is especially high at a distance from the axis of coil where theelectric field reaches its off-axial maximum, and where the “belt” ofhigh current is created around the joint. At the same time the currentalmost does not exist in the segments of the joint where the cartilagelayer crosses the “dead zone”.

Humans have very sophisticated shapes of joints: ball-and-socket jointsin shoulders and hips; hinge joints in fingers, knees, elbows, and toes;pivot joints in the neck and back; and ellipsoidal joints in the wrists.Therefore, it is very difficult, if possible at all, to cover the wholecartilage in a joint with one coil PEMF applicator. It is conceivable,though, creating an applicator that during operation moves from oneposition to another around the joint providing pulsed electric fieldfrom all directions. It is, probably, a good solution of the problem butit requires a relatively complicated piece of electromechanicalequipment that can make the whole PEMF system significantly moreexpensive.

Another solution is to build around the joint an applicator comprising aplurality of coils which generate pulsed electromagnetic field to coverthe joint from multiple places and directions. Arrangement orpositioning of the coils at different places around and under differentangles to the joint allows avoiding overlapping of the dead zones on thetreatment volume. Such an applicator will create a plurality ofdifferent “belts” of current in the cartilage layer with differentangular positions around the joint and can provide full coverage evenfor the most complicated joints. The coils may be activated in sequenceone after another, or in combinations of two or more coilssimultaneously. Also, to create a different pattern of distribution ofthe electric field, directions of the currents in some coils may beswitched in different pulses to the opposite direction.

In the currently available one coil applicators, only axial pulsemagnetic field is used for the coverage of the treatment zone. But, itshould be noted, that at some distance along the coil's axis asignificant component of the magnetic field is being generated and isdirected in the radial direction perpendicularly to the axis of coil. Animproved PEMF device can be provided to efficiently use this radialcomponent for generating pulsed magnetic field and the curly electricfield in the geometric patterns that are not achievable with the axialfield only. The usage of the radial component allows for buildingsophisticated patterns of the electric field to accommodate specialanatomical geometry of the human joints. For example, for a PEMFtreatment of the intervertebral disks the optimum position of a coil isaround the vertebral column. In this position the pulsed magnetic fieldwill be directed along the spine column and the electric field would beapplied circumferentially along the disk. Because the intervertebraldisks are hollow, the dead zone of the coil would not create anyproblem, it would be applied to the hollow part of the disk. So, theposition around the vertebral column seems would be an ideal positionfor the coil. But, anatomically it is impossible.

FIG. 6, discussed above, demonstrates a combination of two coils thatcan create the electric field necessary for the treatment of theintervertebral disks. These two coils are positioned approximately flatin one plane on the back of the patient with their currents directed inopposite directions, clockwise and counterclockwise. Such a combinationof coils creates a pattern of a curly electric field that is appliedcircumferentially along the whole body of the disk with the highestelectric field at the outside edge of the disk where it is most neededbecause that is where the majority of injuries occur.

Temperature of the joint during PEMF treatment is also a factor intreatment efficacy. Articular cartilage does not have its own bloodcirculation and its temperature is less than the body temperature.During exercises, for example running or fast walking, the temperatureof the cartilage of working joints increases up to 2-3 degrees C. Thiselevated temperature gives a boost to metabolism of the joints.Diffusion of nutrients from the blood to the synovial fluid and to thecartilage as well as diffusion of the waste products from the cartilageback to the blood stream increases noticeably. During physical activity,endogenous electrical pulses are applied to the cartilage and causestimulation of its repair mechanism. It is known that arthritis of kneeand hip joints can be reversed to a significant degree by long walkingexercises of the joints. Thus elevated temperature of the cartilage is afactor in the repair process. However, conventional PEMF therapyroutinely is used as a “cold” treatment, without any efforts to providefor elevation of the cartilage temperature.

In the article by Tatsuya Hojo et al “Effect of heat stimulation onviability and proteoglycan metabolism of cultured chondrocytes” (Journalof Orthopaedic Science (2003) 8: 396-399) the authors demonstrated thatexposure of cultured chondrocytes to elevated temperatures 39° and 41°C. for 15 or 30 min had two profound effects on the cells. The firsteffect is the increased viability. As compared to control cultures keptat 37° C. the cells exposed to elevated temperatures had significantlyhigher number of survivors 72 hours after applying the heat stimulation.The second effect is increased proteoglycan metabolism. As compared tothe control cells kept at 37° C., the cultured chondrocytes exposed toelevated temperatures had significantly higher level of proteoglycansfound both inside and outside cells in the culture supernatant. It wasfound also that the cultured cells exposed to 43° C. and higher had bothlower viability and metabolism.

In another publication, Hitoshi Tonomura et al (Journal of OrthopaedicResearch (2008) 26: 34-41) demonstrated that the heat stimulation ofrabbit articular cartilage in vivo caused increase in expression ofextracellular matrix genes of proteoglycan core protein and type IIcollagen, the major structural components of the cartilage. It wasdiscovered also that exposure of the cartilage to higher than 43° C.temperatures caused decrease in the gene expressions of proteoglycancore proteins and type II collagen and increase in expression of heatstress protein (HSP70) instead.

From the natural history of osteoarthritis it is known that theequilibrium in the cartilage turnover between the process of degradationof worn out extracellular matrix and rebuilding it with newproteoglycans and collagen II is tipped to the degradation by inabilityof chondrocytes to produce enough proteoglycans and collagen II—themajor building blocks of the cartilage.

Heat stimulation of the joint increases blood flow around articularcartilage, promotes diffusion of the nutrients to the cartilage andremoval of the waste products from the intercellular space between thecartilage cells. The waste products can be detrimental, even poisonous,especially from not completely healthy or dead cells, plenty of whichare present in the joints affected by arthritis. Exposure to elevatedtemperatures cleans the environment and salvages a lot of compromisedchondrocytes, which would die without it. Notably, heat increasesviability of chondrocytes. By doing this it recruits significantly morecells for participation in the metabolic process triggered by PEMF anddirected to the repair of the cartilage.

At elevated temperatures of 39-41° C., metabolism of chondrocytes issignificantly higher than that at normal joint's temperatures. Thus,PEMF treatment applied to a joint at 39-41° C. will produce moreproteoglycans and collagen II and will repair significantly morecartilage tissue than at normal joint's temperatures, which usually areeven lower than a normal body temperature.

In one aspect, the present new osteoarthritis treatment method anddevice provide for a synergistic combination of heat stimulation andPEMF. The contribution of the heat stimulation to the effect of PEMFtreatment on the cartilage is synergistic because, by changing metabolicrate of chondrocytes, elevated temperatures accelerate the process ofDNA transcription and result in an increase in production of proteinsand other substances needed for the cartilage repair.

As was mentioned before, the healing process in the cartilage istriggered by the electric current flowing in the intracellular spacearound the chondrocytes. When the temperature of the cartilageincreases, so does the electrical conductivity of the intercellularfluid. If an electric field of the same magnitude is applied to a jointat elevated temperatures the current through the cartilage increasesand, hence, the effect of the electric field on triggering the healingeffect. It is an additional synergistic effect that heat stimulationexhibits on the efficiency of PEMF.

Another benefit of performing PEMF treatment at elevated temperature isthe anesthetic effect. It is known from the “Gate theory” of pain thatpain and heat signals from peripheral sensors compete with each otherfor the entrance into the spine. The heat signal has higher priority forpassing through the gate and effectively blocks the signal of a moderatepain from passing into the spine and further to the brain whereperception of pain is formed. Blocking the pain creates relaxation and acomfortable feeling for the user. These qualities benefit acceptance byusers of the new thermally assisted PEMF therapy and creates a positivepreference versus “cold” or “not thermal” PEMF.

As has been mentioned before, one of the objectives of the currentinvention is to keep the joint at elevated temperatures to enhancetherapeutic effect of the PEMF. The preferred temperature to hold thejoint at is in the range of 38 to 41° C. It is undesirable to exceed 42°C., thereby overheating the joint. Elevation of temperature above 42° C.for a significant period of time can cause deterioration of thecartilage and produce more harm than good.

It is known that survival of mammalian cells at elevated temperatures ischaracterized by both the temperature of the exposure and its duration.Different types of cells have slightly different tolerance to heat, butthe basic pattern of cellular response to the heat treatment is similar.A typical graph of the survival of mammalian cells as function of timeof the exposure for different temperatures is shown in FIG. 7. FIG. 7presents a series of survival curves for cells exposed for variousperiods of time to a range of temperatures from 41.5° C. to 42.5° C. Inour case the time of exposure is the treatment time, which is preferablybetween about 30 and 60 minutes, and most preferably between 30 to 45minutes. However shorter and longer treatment times are within the scopeof the invention.

As can be seen from the FIG. 7, in 1 hour time at temperatures 43° C.and above, the number of surviving cells decreases exponentially to asmall fraction of their initial quantity. Below the temperature 41.5° C.all cells survive. Moreover, as has been demonstrated by Tatsuya Hojo etal., the vitality, or survivability, of the chondrocytes at 42° C.increase as compared to that of 37° C. Therefore, the preferred maximumacceptable temperature of exposure for a joint for a 45 minute PEMFtreatment session according to the present invention is 42° C. Thepreferable and effective range of temperatures for a PEMF treatmentsession in the preferred time range according to the present inventionis 39 to 42° C. However, other combinations of therapeutically effectivetemperatures and time ranges may be utilized without departing from thescope of the present invention.

The heat required for keeping the temperature of the joint at 39-42° C.can be generated by several methods. One example is to use the ohmicheat generated by the electromagnetic coils and free wheel diodes placednear or around the joint. In such embodiment, the PEMF applicator to bein thermal contact with the skin around the joint. A layer of a materialwith significant thermal conductivity can be placed between the coilsand the skin to spread the heat from the wires of the coils and the freewheel diodes to the joint and prevent local overheating under the wiresand the diodes. For better heat transfer from a coil to the joint, thecoils and the free wheel diodes may also be imbedded in pads made ofceramics or a potting compound. These pads will serve as thermal bridgesbetween the coils and the joint and can be called heating pads. It isdesirable for the ceramics of the pads to have a high thermalconductivity. This requirement is met, for example, by magnesium orberyllium oxides based ceramics. Silicone RTV may be used as a pottingcompound for flexible applicators. However other materials may be usedthat met these property goals without departing from the scope of theinvention.

An example implementation of the heating pad is shown in FIGS. 8 a and 8b. FIG. 8 a shows a front view of the pad and FIG. 8 b shows a crosssection view of the pad along the line A-A. The heating pad 800 includesa several turn coil 801, a ceramic plate 802 and a free wheel diode 803.Ceramic plate 802 has two surfaces, surface 804 that interfaces thepatient and the opposite surface 805 on which coil 801 and free wheeldiode 803 are secured. The coil 801 is secured to the plate 802 by alayer of ceramic adhesive 806 and free wheel diode 803 by a ceramiclayer 807. Both ceramic plate and ceramic adhesive may be maid ofmagnesium oxide based ceramic similar to the adhesive Ceramabond 471from Aremco Inc. However other materials may be used without departingfrom the scope of the invention. The free wheel diode 803 comprises ofthe diode itself 808 and its heat sink 809.

Ceramic adhesive has high thermal conductivity and provides a goodthermal contact for the diode heat sink 809 with ceramic plate 802. Coil801 is imbedded into ceramic adhesive and also is in a good thermalcontact with the ceramic plate 802. In this embodiment of the PEMFapplicator, all the heat generated in the coil and the free wheel diodeis efficiently transferred to the ceramic plate 802. Numerals 810 and811 designate the terminals of the coil positive and negativecorrespondently, negative end 811 being grounded. Numerals 812 and 813designate the positive and negative terminal of the free wheel diode.They are connected to the terminals of the coil 801. RC filter 814,connected parallel to the coil, performs the function of damping of thehigh frequency oscillations that arise in the circuit when the currentin the coil 801 is interrupted. RC filter 814 effectively suppresselectromagnetic interference resulted from these oscillations.

During a pulse, when the coil is connected to the DC power supply, theenergy delivered by the power supply is spent on the Ohmic heating ofthe coil and creating a magnetic field around it. At the end of thepulse, when the coil is cut off from the DC power supply, the magneticenergy induces an electric current in the circuit made by the coil andthe free wheel diode. One function of the free wheel diode is to protectthe circuitry from the high voltage surge which is created by theinterruption of the current in the coil. In the embodiment discussedherein, both the coil and the free wheel diode are in a good thermalcontact with a ceramic heat sink. This allows not only to collect allthe magnetic energy stored by the coil and use it for the heating of thetreated joint, but also provides good cooling of the free wheel diodeitself, which in turn, allows for achieving very high pulse currents.

To avoid overheating and better control the joint temperature duringPEMF treatment, a temperature sensor or several of them may be placed onthe applicator in the vicinity of the joint. Actual power delivered tothe coils can be controlled by the pulse duration and/or its repetitionrate or just switching the PEMF system on and off. When the temperaturereading reaches the highest value determined by the patient or by thecontroller, the pulsing may be turned off completely, the pulse durationaltered, the repetition rate be changed, or any combination thereof, toallow the applicator to cool down. The physiological feeling ofcomfortable warmth in the joint may also be used as an indication thatthe temperature is right and should not be increased or decreased.

A high frequency generator periodically connected to the electromagneticcoils can be used for the purpose of deep heating of the joints andkeeping their temperatures elevated. In one implementation of the systemwith deep heating, PEMF applicators comprise two coils, the first beinga PEMF coil with a free wheel diode and the second one coupled to a highfrequency generator which is periodically energized to provide deepheating to the joint. The operating frequency of the generator may beabout 10 megahertz or higher in the frequency range where the absorptionof the tissue is high. The temperature of the coil applicator ismeasured by a sensor and provides a feedback to the controller forstabilizing the temperature at a desired level by decreasing orincreasing the operating duty cycle of the high frequency generator.

Another example embodiment of a novel deep heating PEMF systemcomprising a high frequency (HF) generator is shown in the FIG. 9. Forsimplicity of explanation, only one coil is shown in the PEMF system 900depicted in FIG. 9. However it should be understood that the PEMF system900 can comprise a plurality of coils. Numeral 901 designates anapplication coil with a free wheel diode 902 connected parallel to thecoil 901. DC power supply 903 eclectically or functionally coupled witha controller 904 provides pulsed current to the coil 901 in a routinemanner. A HF generator 905 operating in a megahertz range via a wire 906and an electronic or electromechanical switch 907 periodically isconnected to the coil 901. When the generator 905 is connected to thecoil 901, the coil is disconnected from the DC power supply 903. Thevalue of capacitor 908 connected parallel to the coil 901 is selectedfor the LC contour to be tuned in resonance with the frequency of thegenerator 905. The second output wire 909 of the generator 905 isgrounded, as well as the negative pole of the DC power supply 903.

During operation of the system 900, signals from controller 904 viawires 910, 911 and 914 periodically connect to the coil 901, HFgenerator 905 or the DC power supply 903. When the DC power supply isconnected to the coil, the system operates as PEMF. When HF generator905 is connected the coil 901, the joint is heated by the high frequencyelectromagnetic field generated by the coil. To avoid overheating of thejoint its temperature is periodically measured by a temperature sensor913. The reading from the temperature sensor 913 provides necessaryfeedback to the controller for stabilization of the temperature of thejoint.

Now several alternative example PEMF systems with applicators fordifferent parts of a human body will be discussed.

The hand is one part of the human body that is very often affected byarthritis. All the joints in the wrist, fingers and the thumb can beaffected. An embodiment of a PEMF system for treatment of arthritis ofthe hand, including fingers and the thumb, is shown in FIG. 10. Thesystem 1000 comprises an applicator 1001 having a hollow core 1002,outside surface 1003, inside surface defining a hole or aperture 1004and a plurality of electromagnetic coils 1005, 1006, 1007, 1008, 1009,1010 secured on its outside surface 1003. An orthogonal system ofcoordinates XYZ, with axis X positioned along the axis of the applicator1001 and axes Y and Z under 90 degrees to it, is shown in the FIG. 10.

Coils 1005 and 1006 are disposed or arranged around the hollow core 1002at its opposite ends and are designated to generate magnetic field alongthe positive direction of the axis X. Coils 1007 and 1008 are positionedon the opposite sides of the applicator surface 1003 (coil 1007 is notvisible in FIG. 10) to generate magnetic field along the positivedirection of the axis Y; coils 1009 and 1010 generate magnetic fieldalong the axis Z. In this embodiment a pair of coils are designated togenerate magnetic field along each axis X, Y and Z. However, only onecoil is shown in FIG. 10 for axis Y to simplify the drawing. Numeral1015 designates the ends of the coil 1005, numeral 1016—ends of coil1006, numeral 1017—ends of the coil 1007 and numeral 1018—ends of coil1008, numeral 1019—ends of coil 1009; numeral 1020—ends of coil 1010.Also, on the surface of the applicator 1003 a temperature sensor 1021with its ends 1022 is secured. A control unit 1023 via an intermediatemember 1024 is attached to the applicator 1001. All ends of the coils1015 through 1020 and the temperature sensor's ends 1022 are connectedto a multi contact connector 1025.

In another embodiment, instead of two coils on each of axis Y and Z,only one coil on each axis can be employed or three coils positioned at120 degrees around the applicator 1001. The magnetic field created bythe coils inside the applicator 1001 may be substantially non-uniform.The electric field inside the applicator is higher than several mV/cm,preferably about 20 mV/cm.

The connector 1025 is a part of a switching board 1026 which comprises aplurality of “on-off” switches connecting the ends of the coils to a DCvoltage. The DC voltage of 24 Volts is provided by a power supply 1027to the control unit 1023 and to the switch board 1026 via cable 1028.The power supply 1027 itself is powered from an AC grid with a voltageof 110 Volts or 220 Volts.

The switch board 1026 is controlled by a processor 1029, which definesthe sequence and duration of the connection of the coils to DC powersupply and the repetition rate of the cycle. The control unit 1023 has asmall display 1030 for displaying information, such as selected readingsof the temperature sensor 1021. Control unit 1023 also has controlbuttons 1031 allowing to increase or decrease operating temperature ofthe applicator 1001. Alternatively, the control buttons can be providedas screen-actuated buttons on the display 1030. The change in thetemperature of the applicator 1001 is achieved by changing therepetition rate of the cycle of the coil connections.

In one embodiment of the switching board 1100, shown in FIG. 11, all 6coils are connected to the DC power supply via a multi-contact connector1025. One end of each coil 1005-1010 is directly connected to a positivepole 1001, while the other ends are connected to a negative pole 1102indirectly, through a set of 6 high current switches 1103, one switchper end. A set of 6 controlling wires 1104 functionally connect theswitches 1103 with a processor 1029. The processor generates signalsdefining states “on” or “off” of all 6 switches and runs the wholesequence of connections of the coils to the DC power supply. In thisparticular embodiment, all coils can be connected to the DC power supplyparallel to each other, but serial or mixed connections also may beexercised in other embodiments.

The coils may be powered simultaneously in pairs, for example, 1005 and1006 for creating a pulsed magnetic field along the axis X, 1007 and1008 for creating a magnetic field along the axis Y and 1009 and 1010for generating magnetic field along the axis Z. These pulsed magneticfields create curly (rotary) electric fields around axes X, Y and Z andcreate electrical current belts in the cartilage layer of the joints.The direction of these currents follows the directions of the electricfield in the cartilage with their central axes directed along the axesX, Y and Z.

Also, cross-axial pairs of coils can be powered in one pulse. In thiscase the coils positioned in the planes make 90 degrees with each otheras shown in FIG. 12. Here a pair of coils 1201 and 1202 lay in planesmaking 90 degrees with each other. Coil 1201 generates magnetic fieldalong the axis X, coil 1202—along the axis Z. They generate a pulsedmagnetic field 1204 that is a vector sum of the magnetic field generatedby each coil independently and, in FIG. 12, it is represented bycircular loops passing through the interior of both coils 1201 and 1202.The pulsed magnetic field 1204 creates a curly nonuniform electric field1203 that in the treatment zone lies in the plane that makes about 45degrees with both axes of the coils. In the cartilage of the jointpositioned in the treatment zone, a current belt is created with itsaxis turned about 45 degrees to the axes Y and Z.

In FIG. 10 two coils generate magnetic field along each axis X, Y and Z.The treatment zone is located at the center of applicator 1001 betweenthe coils, so one of each pair of coils generates magnetic fielddirected in the treatment zone and the other—out of the treatment zone.In FIG. 10 all coils generating magnetic field directed in the treatmentzone are designated with odd numbers: 1005, 1007, 1009 (“in” coils),while all coils generating magnetic field directed from the treatmentzone are designated with even numbers: 1006, 1008 and 1010 (“out”coils).

For the most efficient generation of pulsed magnetic field in thetreatment zone and hence the therapeutic electric field, for cross axialpulsing, “in” coils of one axis can be synchronously pulsed with “out”coils of another axis. In this combination, magnetic field from one coilwill not partially compensate the magnetic field of the other coil andthe resulting electrical field in the treatment zone will be maximal.All possible combination of “in” and “out” coils can be used forpulsing. Possible cross axial combinations of coils are: 1005-1008,1005-1010, 1006-1007, 1006-1009, 1007-1010, 1008-1009, total 6. Threeaxial combinations for axes X, Y and Z make it total 9 combinations.

The PEMF applicator exhibited in FIG. 10 therefore provides curlelectric field covering the treatment zone from nine differentdirections: along the axes X, Y, Z plus six directions making about 45degrees with the axes X, Y, Z. In comparison with a one coil applicatorthe coverage of the joints with electric field is significantlyimproved. After a full cycle of nine pulses with different spatialdistributions the applicator does not leave untreated any part of thecartilages of the wrist, fingers or the thumb.

In FIG. 13, another embodiment of a multi-coil applicator 1300 of thepresent invention is exhibited. This embodiment is configured fortreatment of the back pain. Back pain has two major origins:degeneration of the intervertebral discs and arthritis of the facetjoints. The intervertebral disc is a cartilaginous structure thatresembles articular cartilage in its biochemistry. The facet joints arelocated in the back portion of the spine. Two facet joints combine withthe intervertebral disc to create a three-joint complex at eachvertebral level. The facet joint consists of two opposing bony surfaceswith cartilage on their surfaces and a capsule around them. The capsuleproduces synovial fluid to lubricate the joint. The facet jointarthritis causes inflammation and breakdown of the cartilage and resultsin stiffness and chronic or acute pain of the joint.

In FIG. 13, depicting the back applicator 1300, four PEMF coils 1301,1302, 1303 and 1304 are disposed on a flexible belt 1306 to securablyplace the coils adjacent the patient's back. At the center of the backapplicator 1300 a temperature sensor 1305 is also positioned. In anotherembodiment temperature sensors may be placed near each coil of theapplicator. The belt 1306 has a buckle 1307 and the opposite free end1308. Two harness strips 1309 and 1310 secured to the belt 1306 at itsupper central part with first ends and the second ends engaged withbuckles 1311 and 1312. The middle part of the harness strips go over theshoulders of the patient 1313 and 1014. The belt 1306 and the harnessstrips 1309 and 1310 allow positioning the four PEMF coils at a selectedheight and securing it against the treatment site. All wires 1315 fromthe coils and the temperature sensor connected to a multi contactconnector 1316 which is a part of a switching board 1317.

In one embodiment the switching board 1317 includes a plurality of“on-off” switches to connect and disconnect the ends of all coils to andfrom positive and negative poles of a DC power supply to provideelectric currents in the coils in clockwise and counterclockwisedirections independently in all four coils. In this embodiment theswitching board may have as many as 16 switches, two switches per oneend of a coil for connecting to positive and negative poles of the DCpower supply. The DC voltage, 12 or 24 Volts is provided by a powersupply 1021 to processor 1318 and switch board 1317 via connector 1319and cable 1320. The power supply 1321 itself is powered from normalhousehold outlets, such as 120 or 220 Volts AC.

The switching board 1317 is controlled by a processor 1318 which definesthe sequence, polarity, duration of the connections of all coils to theDC power supply and the repetition rate of the cycle. The processor 1318is also functionally connected to the temperature sensor 1305. Thetemperature of the applicator selected by the patient is maintained bythe processor 1318 via selection of the repetition rate of pulsing.Numeral 1322 is a display showing a selected temperature of theapplicator. The display also has control buttons 1323 allowing toincrease or decrease operating temperature of the applicator. Placingboth the temperature display 1322 and control buttons 1323 in the powersupply 1321 is optional; they can be as well placed in the processor1318, on a remote control, or on the applicator.

In a further embodiment of the applicator, instead of switching coilsfrom one polarity to the other to change direction of the current in it,two coils wounded in opposite directions, clockwise andcounterclockwise, can be used. The switchboard for this embodiment isschematically shown in FIG. 14. Here 1401 and 1402 are two coils withopposite windings; 1403 and 1404 are positive and negative poles of theDC power supply. High current switches 1405 and 1406 connect the coilsone at a time to the positive pole 1403 for a preselected time of pulse.Because the opposite ends of the coils are connected permanently to thenegative pole, every connection of a coil to the pole 1403 results in acurrent pulse through this coil. Coils 1401 and 1402 generate a magneticfield of opposite directions. Numerals 1407 and 1408 designate highcurrent diodes which via switches 1409 and 1410 are connected to theends of the coils. These diodes, called “free wheel” diodes, function toprotect the circuitry from a transient high voltage peek arising at theends of a coil when the current sharply collapses after disconnectingthe coil from the power supply. The switch 1407 is turned into on-offstates synchronously with the switch 1405, and respectively, switch 1410is synchronized with the switch 1406. The energy of the magnetic fieldstored by the coils smoothly dissipates in the diodes 1407 and 1408 andthe wires of the coils and the transient voltage peek in this case doesnot exceed a fraction of the DC voltage.

FIG. 15 depicts yet another embodiment of the back applicator 1500. Thecoils 1511-1514 are shown attached to the ceramic pad 1501-1504. In thisconfiguration, coils 1511 and 1513 are switched on simultaneously; theyare intended for application of the curl electric field to theintervertebral disk. Coils 1512 and 1514 are intended for application ofthe curl electric field to the facet joints and are also switchedtogether when the coils 1511 and 1513 are off. In this arrangement, themagnetic filed of coil 1514 is directed into the page while the magneticfield of coil 1512 is directed out of the page. Temperature sensors maybe placed at each ceramic pad 1501-1504

FIG. 16 schematically exhibits a segment of human spine 1600 andelectromagnetic field covering an intervertebral disk and facet jointsfor the PEMF applicator shown in FIG. 13. Here 1301, 1302, 1303 and 1304are coils of the PEMF applicator. During a pulse, coils 1301 and 1302generate magnetic field in the direction of the spine and coils 1303 and1304 in the opposite direction, from the spine. 1601 and 1602 arevertebras with intervertebral disk 1603 between them. 1604 is one offacet joints between the two vertebras; the second one, situated at thesame level symmetrically with the joint 1604 is not seen in the figure.Magnetic field generated by the coils is shown on the segment of thespine with curve lines 1605. Curl electric field is shown by circularlines 1206. The electric field lines lie in the plane of theintervertebral disk 1203 and follow it circumferentially. Thus, theelectric field configuration is optimized for the PEMF treatment.

FIG. 17 exhibits another embodiment of a PEMF applicator. The depictedopen-fingered “glove” type applicator 1700 is configured for treatmentof the wrist and thumb of the hand. The glove applicator 1700 includesor comprises two layers of elastic fabric 1701 and 1702 that cover thewrist 1703 and the thumb 1704 of the hand. The inner layer of the glove1702 is seen in the cut-away portion of the upper layer that alsoexposes PEMF coils 1705, 1706 and 1707. Coil 1705 is wound around thewrist 1703; coil 1706 around the thumb 1704 and the coil 1707 isattached at the middle part of the back of the hand. A temperaturesensor 1708 is disposed on the inner layer of the glove between thecoils. Numeral 1715 designates the ends of the coil 1705; numeral 1716designates the ends of the coil 1706; numeral 1717—the ends of the coil1707 and numeral 1718 the ends of the temperature sensor 1708. The endsof all three coils and the temperature sensor are connected to a multicontact connector 1719 which is a part of the switching board 1720.

The switching board 1720 is functionally connected to a processor 1721which defines the sequence of pulsing of the coils. The switching board1720 and processor 1721, via a cable 1723, are powered by DC powersupply 1724. Processor 1721 has up-and-down buttons or knobs 1725 forselection by the patient higher or lower operating temperature of theapplicator. Other patient input means, such as contact sensors orswitches are also included within the scope of the invention.

While the coils can be actuated in any effective manner, the preferredsequence of activation of the coils is: single coil pulses though coils1705, 1706 and 1707; double coil pulses trough coils 1705-1706, coils1705-1707, and coils 1706-1707. In this case the coils 1705 and 1706 maybe connected to the switching board 1720 as one direction coils.

In one preferred example, the magnetic field in coil 1705 is directedinto the treatment zone and magnetic field in coil 1706—always out ofthe treatment zone. In their simultaneous pulse they deliver to thetreatment zone a strong magnetic field that enters into the treatmentzone through coil 1705 and leaves through the coil 1706. Coil 1707 is atwo direction coil and is connected to the switching board 1720 withseveral switches, enabling controller 1721 to run the pulses in bothdirections and makes possible strong magnetic field pulses in both pairs1705-1707 and 1706-1707. All coils of the applicator 1700 have lownumbers of turns, generally less than ten, preferably 4-5 turns. Formechanical compatibility with elastic fabric the coils can be made offlexible multi strand conductors with diameters of the wires around100-200 micrometers. Overall cross-section of a conductor is about 2-3mm². In FIG. 17, some of the coils are shown as being “wavy.” Thewaviness indicates elastic properties in the coils, including somespring action, so that they can be easily taken on and off the hand aspart of the applicator.

FIG. 18 depicts a PEMF knee applicator 1800 according to a furtherembodiment of the invention. The applicator 1800 includes two layers ofelastic fabric, the outer layer 1801 and inner layer 1802 which is seenin the cutaway portion of the outer layer. The upper end of theapplicator 1803 is positioned above the knee 1805 and the lower end 1804is below the knee 1805. Five PEMF coils are in the applicator 1800.However a larger or smaller number may be used.

Coil 1806 is wounded around the leg above the knee; coil 1807 below theknee; coil 1808 is placed around the patella of the knee and the coils1809 and 1810 are at the right and left sides of the knee, coil 1810 isnot seen in the FIG. 18. Numeral 1811 designates a temperature sensorpositioned between the coils on the inner layer 1802 of the applicator.The ends of all five coils marked by numerals 1816, 1817, 1818, 1819,1820 and the ends 1821 of temperature sensor are connected to a multicontact connector 1822 which is a part of, or is functionally connectedto, a switching board 1823.

The switching board 1823 is controlled by a processor 1824, whichdefines the sequence of connecting ends of coils to a DC power supply1826 and the repetition rate of the cycle. Processor 1824 has pushup-and-down buttons 1825 that allow the patient selecting an operatingtemperature. However any other button, actuator or switch known topersons skilled in the art may be used. The operating temperaturechanges by changing repetition rate of the cycle or the duration ofpulses in the coils. A DC power supply 1826, via a cable 1827, isconnected to the processor 1824.

Multiple patterns of pulsing may be selected for the PEMF treatment ofthe knee with this applicator. Some coils, for example, coils 1806 and1807 can be connected to a switching board as one direction coils, somecoils can be connected as two direction coils, for example coils 1808,1809, and 1810. A one direction coil 1904 with protective free wheeldiodes can be connected to the DC power supply as shown in FIG. 19.

In FIG. 19 numerals 1901 and 1902 are positive and negative poles of theDC power supply; 1903 through 1911 are high current semiconductorswitches, 1904 and 1912 are PEMF coils; 1905, 1913 and 1914 areprotective free wheel diodes. The diodes function is to protect theelectronic circuitry from a high voltage surge that takes place when thecoil is disconnected from the DC power supply and its current collapses.A diode is connected parallel to the coil with its open directionagainst the DC voltage, so during the pulse there is no current in thediode. When the coil is disconnected from the power source, the currentcollapses and at the ends of the coil a high voltage surge of oppositedirection appears due to the self inductance of the coil. The diode isthen open for this direction and a current flows around the circuit madeof the coil and the diode. If a protective diode is employed, thevoltage on the coil during collapse of the current can be several timesless than that of the DC power supply. When switches 1906, 1909 and 1910are open and the rest of them are closed, coil 1912 generates magneticfield of one direction; when these switches are closed but switches1907, 1908 and 1911 are open, the coil 1912 generates magnetic field inopposite direction. The two direction coil 1912 can be connected to theDC power supply as shown in FIG. 19. The two directional coils in onealternative embodiment may be made of two coils wounded in differentdirections (clockwise and counter clockwise) and connected to DC powersupply as shown in FIG. 14.

Another implementation of a hand PEMF applicator is schematically shownin FIG. 20. Here are shown the right hand 1 with thumb 2 and wrist 3 andthe left hand 4 with thumb 5 and wrist 6. Essentially cylindrical sleeve7 of the applicator comprises at least two layers of fabric, inside 8and outside 9 layers which are secured coaxially to each other. Thesleeve 7 has front side 10 and rear side 11 and openings 12 and 13 forinserting right and left hands correspondently. The applicator 20 mayhave a belt 14, secured to the rear side 11 of the sleeve 7 and intendedfor attaching applicator 20 to the patient's waist by a buckle 15.

Between the layers 8 and 9 inside sleeve 7 a number of electromagneticcoils and heating pads are secured adjacent to the joints of the handswhich frequently are subjects to osteoarthritis. Coil 16, made of veryflexible multi strand wire, is secured between layers of fabric 8 and 9around the right wrist 3; heating pad 17 is placed in a pocket betweenlayers of fabric 8 and 9 in a vertical position in physical proximity towrist 3. Similarly, coil 18 is secured around the left wrist 6 andheating pad 19 is placed adjacent to left wrist 6. Coil 20, encapsulatedin a high thermal conductivity ceramics, is attached to heating pad 21with a ceramic adhesive and positioned in a pocket on the rear side 11of the sleeve 7 proximal to the left thumb joint 5. Coil 22 and heatingpad 23 in a similar way are attached to each other and positioned at theright thumb joint correspondently. Coil 24 and heating pad 25 are placednear finger knuckles 26 in a pocket on the front side 10 of the sleeve7. All wiring from the coils 16, 18, 20, 22, 24 and thermal sensors onall heating pads, not shown in FIG. 20, are combined in a cable 27 whichis connected to the programmable controller 28.

Controller 28 provides pulsing currents into coils in a predeterminedsequence in time and stabilizes the temperatures of the heating pads bychanging repetition rate of the pulsing. Controller 28 is provided witha knob 29 for turning device on and off and selecting temperature of theheating pads. Display 30 provides information about selected temperatureand the process of treatment. Cable 31 connects control unit 28 to a DCpower supply which in turn is powered from AC grid by a cable 33.

Directions of magnetic field B and induced electric field E, provided byeach coil, are schematically shown in FIG. 20 by straight and circulararrows. There are two phase of pulsing cycle in the device. In thefirst, coils 16 and 18 are powered simultaneously and provide magneticfield in direction along the hands. In the second, coils 20, 22 and 24are powered and provide magnetic filed in direction perpendicular to thehands. Each cycle may have duration from several seconds to several tensof seconds. Duration of each individuals pulse may be from several tensof microseconds to several hundreds microseconds. Overall treatment timepreferentially may vary from 0.5 to 1.0 hour.

Each coil has a protective “free wheel” diode connected in parallel tothe coil and attached to corresponding heat pad by a high thermalconductivity ceramic adhesive. This feature of the design improvescooling of the “free wheel” diode and transports heat deposited in it tothe heating pads.

Referring to FIG. 21, knee applicator 100 comprises the body of theapplicator 104 covering the knee 101 and stretching between the thigh102 above the knee and the lower leg 103 below the knee. Numeral 105designates the upper end of applicator and numeral 106—its lower end.Numeral 107 designates the upper wide belt; 108 is the upper narrowbelt, both belts on the upper end of the applicator above the knee. Thetwo belts wide 107 and narrow 108 secure the applicator 100 to the thigh102 by a Velcro hook-and-loop fastener. However other suitable fastenersmay be used.

The Velcro hook-and-loop fastener comprises two elongated fabric stripswhich are attached (sewn, adhered, etc) to the opposing surfaces betweenthe belts 107 and 108, one of which contains multiple hooks and theother—loops. (Not shown in the FIG. 21). The low end of the applicatoris secured over the low leg 103 by two belts 109 and 110 with two Velcrofasteners between them (not shown). In a cutoff 111 in the upper part ofthe applicator an electromagnetic coil 112 is schematically shown with athermal sensor 113 secured to it, said thermal sensor is designated formonitoring the temperature of coil 112 and surrounding. The details ofhow the coil 112 and the thermal sensor are positioned in the applicatorwill be shown below in FIG. 22.

Similar to the upper end of the applicator, at the lower end in thecutoff 114 an electromagnetic coil 115 with a thermal sensor 116 securedto it. In the cutoff 117 a coil 118 and the thermal sensor 119positioned at the knee patella (not shown) are schematically depicted.When activated, coil 112 above the knee applies a magnetic field alongthe thigh 102; the coil 115—along the lower leg 103 and the coil118—perpendicular to the patella at the top of the knee.

Coils 112 and 115 are connected in parallel to another output ofcontroller 124 via two high current wires 120 and 121. Coil 118 isconnected to controller 124 via two high current wires 122 and 123.Thermal sensors 113, 116 and 119 communicate with controller 124 viadouble wires 125, 126 and 127. The wire 120 optionally may comprise aconnector 128 which gives an opportunity to disconnect one end of coils112 and 115 from a controller 124 and comfortably place the applicator100 around the knee before treatment. For treatment, wire 120 ispreferably reconnected to the coils 112 and 115 of the applicator.During wrapping the applicator around the knee, the connector 128 ispreferably in a disconnected state. The disconnection of connector 128allows performing placement of the applicator around the knee withoutcreating an additional loop of high current wire 120 that can distortthe electromagnetic field generated by coils 112 and 115.

Controller 124 includes a control knob 129 which turns on and off thePEMF system and allows selecting a treatment temperature of theapplicator by the user. Light diode indicator 130 shows the electedtemperature of the treatment. Controller 124 may be secured to a thighor waist belt, not shown at the FIG. 21. Controller 124 is powered by aDC power supply 131 connected to an outlet of the power grid, or byother suitable power supply.

FIG. 22 schematically depicts the applicator 100 in an unwrapped state200. All numerals in FIG. 22 that correspond to the parts visible inFIG. 21 are identical. New numerals in FIG. 22 are described below.Unwrapped applicator 200 is shown with a cut off in a fabric 207covering inside surface of the applicator. Coil 112 at the upper part ofthe applicator has two ends 201 and 204. Coil 115 at the lower part ofthe applicator has two ends 202 and 205. These two coils are connectedin parallel by a high current wire 203 which connects ends 201 and 202and a high current wire 206 which connects ends 204 and 205. Wires 120and 121 connect the parallel coils 112 and 115 to the controller 124shown in FIG. 21. Wire 120 with connector 128 and wire 121 in FIG. 22are depicted at the horizontally opposite ends of the applicator butafter wrapping the applicator around the patient's knee the wires 120and 121 will appear close to each other as shown in the FIG. 21. Numeral208 designates two Velcro strips secured on the inner fabric layer 207of two narrow belts 108 and 110. The matching Velcro strips that engagestrips 208 in a wrapped around the knee applicator are attached to theexternal side of wide belts 107 and 109 and are not seen in FIG. 22.

FIG. 23 illustrates certain different embodiments of coils 112 and 115in an unwrapped state. All three embodiments 301, 302 and 303 aresubstantially flat in the plane of the drawing. Embodiment 301 is achain of small coils having several turns each (exemplary 2 to 4) andconnected serially. Embodiment 302 is a multi turn spiral flattened inthe plane of the drawing. Embodiment 303 comprises a meander shapedwire. All three coils 301, 302 and 303 comprise high current solid ormultistranded wires with the conductor diameter between 1 and 2 mm.

When a coil 301, 302 or 303 is wrapped circumferentially around a thighor low leg it creates a magnetic field along its axis (and inside theknee volume) that is substantially equivalent to the magnetic field of asimple one turn coil made of a bent wire. Even though this simple oneturn coil makes the knee applicator simple and easy to manufacture, ithas a very low inductance (small fraction of a microHenry), which makesit very difficult to achieve electromagnetic pulses in the range of tensof microseconds, as desired by the PEMF treatment system.

All coils depicted in FIG. 23 comprise wires several times (e.g. threeto five) longer than that of a simple one turn coil and havesignificantly higher inductance, in the range of 5 to 10 microHenry,which is sufficient for preferred duration of pulses in a PEMF system(20 to 50 microseconds). So, the higher inductance of the coils shown inFIG. 23 is advantageous in PEMF applicators as compared with applicatorsemploying a simple one turn coil. Another advantage of the coilsdepicted in FIG. 23 is that they have significantly larger surface areathat provides better conduction of ohmic heat generated in the coils tothe treatment area versus simple one-turn coils.

When interrupted at the end of a pulse, the electric current throughPEMF coils creates a very high spike of voltage between two ends of thecoils. This spike can be as high as hundreds to thousands volts, and ifnot dealt with, it can damage the insulation of the coils and/or thecontroller of the system. As disclosed in U.S. patent application Ser.No. 12/878,028, this problem may be solved by adding a “free wheel”diode in parallel to the PEMF coils. The free wheel diode reduces thevoltage spikes to safe 20-30 volts and redistributes the magnetic energystored of the coils between the coil and the free wheel diode itself.

For efficient generation of electric field in the treatment area by aPEMF system it is preferred to use pulses with duration about ¼ or lessof the time of relaxation of the coil τ=L/R. Here L is the inductance ofthe coil and R—its resistance. In this case the heat is distributedabout equally between the coil and the diode. For longer than ¼ of thetime of relaxation pulses the heat is deposited mainly in the coil andthe diode remains relatively cool.

In certain embodiments, the pulse duration is preferred to besignificantly longer than ¼ of the time of relaxation and the free wheeldiode be placed in the controller. That further simplifies the designand manufacturing of the knee and neck applicators.

A neck applicator 400 is schematically depicted in FIG. 24. The body ofthe applicator 401 is positionable around the neck 402. Numeral 403designates the upper end of the applicator and numeral 404—its lowerend. The applicator is secured to the neck 402 by a belt 405 with aVelcro hook-and-loop fastener that is not seen in FIG. 24. It will bedescribed in FIG. 25. The Velcro hook-and-loop fastener comprises twoelongated fabric strips which are attached (sewn, adhered, etc) to theopposing surfaces of the applicator 401 and belt 105, one of whichincludes multiple hooks and the other—loops. (Not shown in the FIG. 24).In a cutoff 406 in the applicator an electromagnetic coil 407 isschematically shown with a thermal sensor 409 secured to it. A thermalsensor 410 is secured to electromagnetic coil 408. The thermal sensors409 and 410 are designated for monitoring temperatures of coils 407 and408 and their surroundings. When activated, coils 407 and 408 applymagnetic field in the direction along the neck 402.

Coils 407 and 408 comprise high current solid or multi-stranded wireswith the conductor diameter between 1 and 2 mm. They are connected inparallel to an output of controller 411 via two high current wires 412and 413.

Thermal sensors 409 and 410 communicate with controller 411 via doublewires 414 and 415. Controller 411 includes a control knob 416 whichturns on and off the PEMF system and allows selecting a treatmenttemperature of the applicator by the user. Light diode indicator 417shows the elected temperature of the treatment. Controller 411 may besecured to a waist belt 418. Controller 411 is powered by a DC powersupply 419 connected to an outlet of the power grid by a connector 420,or other suitable power source.

FIG. 25 schematically depicts the neck applicator 450 in unwrappedstate. All numerals in FIG. 25 that correspond to the parts visible inFIG. 24 are identical. New numerals in FIG. 25 are described below. Coil407 and coil 408 are connected in parallel at their ends 453 and 454 byhigh current wires 412 and 413. Numeral 451 designates a Velcro stripsecured on the belt 405. The matching Velcro strip that engages thestrip 451 in a wrapped state of the neck applicator is attached to theexternal side of the neck applicator near its wide end 452 it is notseen in FIG. 25.

Various embodiments of the coils 407 and 408 are shown in FIG. 23. Thesame way as with the knee applicator, when coils 407 and 408 are wrappedcircumferentially around neck 402 they create a magnetic field along andinside the neck that is substantially equivalent to the magnetic fieldof a simple one turn coil wound around the neck. As was stated above,such a one turn coil would have a very low inductance (small fraction ofa microHenry), which makes it very difficult to achieve electromagneticpulses in duration in the range of tens of microseconds, as preferred bythe PEMF system. Both coils 407 and 408 are made of wires several times(three to five) longer than that of a simple one turn coil around theneck and have significantly higher inductance, in the range of 5 to 10microHenry, which is sufficient for preferred duration of pulses in thePEMF system (20 to 50 microseconds).

The coils shown in FIG. 23 also have significantly larger surface areathan that of a one turn coil and provide better conduction of ohmic heatgenerated in the coils to the treatment area of the neck.

For convenient placement of the neck applicator it does not needdisconnection of its wire 412 or 413, it can be easy placed over thehead by the user.

Other configurations of applicators may be utilized depending on thejoint of the person that is to be treated. For example, foot, ankle,shoulder, elbow and hip applicators may be provided.

It is also within the scope of the invention to combine features,functions, advantages and aspects of the various embodiments describedherein. Thus the embodiments of the invention may comprise combinationsof aspects of any one or more of these exemplary embodiments.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred exampleembodiments, it will be apparent to those of ordinary skill in the artthat the invention is not to be limited to the disclosed exampleembodiments. It will be readily apparent to those of ordinary skill inthe art that many modifications and equivalent arrangements can be madethereof without departing from the spirit and scope of the presentdisclosure, such scope to be accorded the broadest interpretation of theappended claims so as to encompass all equivalent structures andproducts.

For purposes of interpreting the claims for the present invention, it isexpressly intended that the provisions of Section 112, sixth paragraphof 35 U.S.C. are not to be invoked unless the specific terms “means for”or “step for” are recited in a claim.

What is claimed is:
 1. An apparatus, comprising: an applicator; anelectromagnetic coil provided to the applicator; a free wheel diodeprovided to the applicator and electrically connected in parallel withthe electromagnetic coil; a controller functionally connected to theelectromagnetic coil, the controller configured to electrically pulsethe electromagnetic coil to generate a plurality of electromagneticpulses; a power source electrically connected to the controller; atemperature sensor disposed in the applicator and functionally connectedto the controller, wherein the free wheel diode is configured togenerate heat in the applicator in response to the pulsing of theelectromagnetic coil, and wherein the controller configured to change arepetition rate of the pulsing to maintain a predetermined temperatureof the applicator.
 2. The apparatus as in claim 1, wherein theapplicator is configured to be secured to a knee of a patient.
 3. Theapparatus as in claim 1, wherein the applicator is configured to besecured to a torso of a patient.
 4. The apparatus as in claim 1, whereinthe applicator is configured to receive both of a patient's handssimultaneously.
 5. The apparatus as in claim 1, wherein thepredetermined temperature is in a range of 38 to 42 degrees C.
 6. Theapparatus of claim 1, wherein the controller is configured to change aduration of the electromagnetic pulses.
 7. The apparatus of claim 1,wherein the electromagnetic coil comprises less than 50 turns ofconductive wire.
 8. The apparatus of claim 1, wherein theelectromagnetic coil includes 1 turn to 10 turns of conductive wire. 9.The apparatus of claim 1, wherein the controller is configured to varythe repetition rate of the pulsing in the range of 10 to 1000 Hertz. 10.The apparatus of claim 1, wherein the electromagnetic coil and the freewheel diode are imbedded in a high thermal conductivity ceramic.
 11. Theapparatus of claim 1, further comprising a display and a user-actuatabletemperature control coupled to the controller.
 12. The apparatus ofclaim 1, further comprising a plurality of electromagnetic coils and aplurality of free wheel diodes provided to the applicator, wherein eachof the plurality of electromagnetic coils is electrically coupled to arespective one of the plurality of free wheel diodes.
 13. A method fortreating arthritis in a joint of a human, the method comprising:disposing an applicator adjacent to the joint to be treated; receivinginput by a processor indicating a desired therapy temperature;generating a pulsed electromagnetic field in the joint by energizing anelectromagnetic coil; terminating the pulsed electromagnetic field;dissipating a quantity of energy in the electromagnetic coil byconverting the quantity of energy to heat within the applicator; heatingthe joint to be treated to a temperature in the range of 38-42 degreesC.; and adjusting a parameter of the pulsed electromagnetic field togenerally maintain a set therapy temperature.
 14. The method of claim13, wherein the step of adjusting a parameter of the pulsedelectromagnetic field comprises changing a repetition rate of the pulsedelectromagnetic field.
 15. The method of claim 13, further comprisingperforming treatment for a time range of 30 to 60 minutes.
 16. Themethod of claim 13, wherein the pulsed electromagnetic field generatedin the joint is in a range of 1 to 100 mV/cm.
 17. The method of claim13, further comprising securing the applicator to the human to maintaina predetermined orientation of the pulsed electromagnetic field withrespect to the joint.
 18. A system, comprising: an applicator includingan electromagnetic coil disposed therein; a controller; a temperaturesensor disposed in the applicator; a display configured to indicate aselected therapy temperature and a state of treatment; a power sourcecoupled to the controller and the electromagnetic coil; and a heatsource disposed in the applicator, the heat source comprising a freewheel diode electrically connected to the electromagnetic coil, whereinthe controller is configured to pulse current into the electromagneticcoil in a predetermined sequence in time and to change a repetition rateof the pulsing to generally maintain the selected therapy temperature.19. The system of claim 18, wherein the applicator comprises a ceramicpad, and wherein both the coil and the free wheel diode are disposed inthe ceramic pad.
 20. The system of claim 18, further comprising aplurality of electromagnetic coils and a plurality of free wheel diodesprovided to the applicator, wherein each of the plurality ofelectromagnetic coils is electrically coupled to a respective one of theplurality of free wheel diodes.